Audio Spectrum Analyzer TM

llad1e lhaeK A DIVISION OF TANDY CORPORATION

FORT WORTH. TEXAS 76102

Audio Spectrum Analyzer™ Program:

©1981 Data Soft Inc.

Licensed to Tandy Corporation

All Rights Reserved.

This applications software for the TRS-80 Color microcom

puter is retained in a read-only memory (ROM) format. All por

tions of this software, whether in the ROM format or other

source code form format, and the ROM circuitry, are

copyrighted and are the proprietary and trade secret informa

tion of Tandy Corporation and/or its licensor. Use, reproduc

tion or publication of any portion of this material without the

prior written authorization by Tandy Corporation is strictly pro

hibited. The license for using this software is printed in the

back of this manual.

Audio Spectrum Analyzer™ Program Manual:

©1981 Tandy Corporation

All Rights Reserved.

Reproduction or use, without express written permission from Tandy Corporation, of any portion of this manual is prohibited.

While reasonable efforts have been taken in the preparation of this manual to assure its accuracy, Tandy Corporation

assumes no liability resulting from any errors or omissions in

this manual, or from the use of the information obtained

herein.

10 9 8 7 6 5 4 3 2 1

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Recommended Input Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Starting Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Real-time and RMS Display Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Peak Hold and Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Freezing the Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Audio Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Kaleidoscope Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Measuring the Electronic Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Measuring the Audio Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Summary of Key Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Introduction

To the audio purist, high fidelity is a term which means faithful sound

reproduction-the sound of "being there." Full, rich, accurate sound

every nuance precisely delineated. The tools to reach this desirable goal

have been available for years. Quality amplifiers, tuners, turntables,

receivers, and speakers, designed for maximum fidelity are available in

almost every price range. All of these come supplied with impressive

specifications and overwhelming claims.

But specifications and charts tell only part of the story. How well do these

individual parts work together? The Radio Shack Audio Spectrum AnalyzerTM

for the Color Computer can help you achieve the maximum possible perfor

mance from your audio investment. It allows you to watch the music, show

ing you the power distribution of the music, or if you prefer, provides a

visually entertaining Kaleidoscope of changing, dancing patterns for hours

of relaxation.

The Audio Spectrum Analyzer is designed to analyze a 9 octave audio range,

using vertical color bars to represent twenty seven V3 octave segments,

beginning at 31.5 Hz and ending at 12,500 Hz, using ISO standard frequen

cies as V3 octave points. The center frequencies (in Hertz) are:

31.5 40 50 63 80 100

125 160 200 250 315 400

500 630 800 1000 1250 1600

2000 2500 3150 4000 5000 6300

8000 10000 12500

1

2

The bars are calibrated in dB, referenced to a suitable level for audio input.

The measurement level extends from - 20 dB to + 5 dB. It will show a max

imum level that is over 256 times louder than the softest measured sound.

Technical Note: Since program sources can vary greatly in average level, the

Spectrum Analyzer is designed to scale the range relative to the loudest

note that is currently playing. This feature insures the greatest relative

deviation will always be shown. Many analyzers will simply cease to show

most of the audio range if the signal level drops too low. The Spectrum

Analyzer automatically locks onto the loudest note, then shows the

response relative to that note.

Recommended Input Sources

Test Required Equipment

Amplifier Response 1/4" Stereo Jack to 1/8" Miniplug (Radio Shack

#274-363)

Optional 1/8" to 1/8" Extension Cord (Radio

Shack #42-2472

Audio Response Realistic 33-1058 Tie Clip Mike

Radio Shack 277-1008A Miniamp

Audio signals must enter the computer via the black cassette recorder jack.

Normal operating range extends from V2 watt to 10 watts, at 220 Ohms. Very

low impedance sources (8 Ohms and below), such as the direct speaker out

puts on your amplifier, can distort your readings and possibly damage your

computer.

Use a low level source {e.g. headphone jack, cassette earphone jack, or the

output from a low-powered amplifier, such as the Radio Shack 277-1008A

Miniamp, which can be driven by a Realistic 33-1058 Tie Clip Mike for room

measurements).

3

4

Starting Up

Make sure the computer is correctly connected to the TV set and the set is

tuned to the right channel (3 or 4). With the computer off, insert the Spec

trum Analyzer cartridge in the slot on the right side of the computer. Turn

the TV and computer on. The Spectrum Analyzer program title will appear.

Press any key to start the program. If you do not press a key, the program

will automatically start in about 30 seconds.

Real-time and RMS Display Modes

Press [£] for the Fast Real-Time response (Peak) mode, to show the instantaneous energy distribution of the music and evaluate the peak energy re

quirements. The program always starts in the Fast mode. Press � for averaging Slow response (RMS) mode, to measure the effect of speaker

placement or tone adjustments.

Detail

The display shows the frequencies (in octave steps) near the bottom of the

screen. This allows a quick reference to show general frequency distribu

tion and level, showing only octave markers. Press [Qj to see the Detailed VJ octave display.

The detailed V3 octave display allows a complete analysis by displaying all

27 frequency bands simultaneously over the entire 9 octave range covered

by the Spectrum Analyzer. Press [OJ again to return to the full octave steps.

Peak Hold and Reset

Measuring power is a normally difficult task. Peaks in the music pass very

quickly. The Spectrum Analyzer has the ability to lock onto the highest peak

level reached in each band. In the Fast mode, you can quickly see which fre.

quencies demand the most power. In the Slow mode, the Peak Hold in

dicator can show the average distribution of the signal and the general

relative response of the system under test.

Press @] to show the Peak levels in the signal. To Reset the Peak indicator, press the IBl key at any time. You can turn off the Peak Hold function by pressing @] again.

Freezing the Display

There are times when it is very desirable to be able to analyze a musical

passage or one instant in time. Pressing the Space Bar in either mode

freezes the display to show the response at the moment the Space Bar was

pressed. Pressing any key restarts the display.

5

6

Audio Option

When connected to the earphone output jack of a cassette recorder, the

built-in speaker in the recorder is turned off. To hear the music under test,

there is a feed-through Audio option that lets you hear the signal through

the TV sound amplifier. Press [Al for Audio. This feature can be switched off by pressing [Al again. This option can only be set in the Graph mode.

Kaleidoscope Mode 6

Press [Kl for the built-in audio Kaleidoscope (color organ) to produce random changing visual images, keyed to the audio signal's frequency distribu

tion and intensity. Press [§] to return to the Graph mode.

Measuring the Electronic Chain

Connect the black earphone plug to the headphone output jack on your

amplifier. Use a familiar record as your measuring tool. All tone altering con

trols should be set to flat response. Set the volume level to a position slight

ly louder than most people would consider normal listening level for middle

of the road (MOR) music. Set the Spectrum Analyzer to Slow response with

the Peak display turned off.

Play the entire selection, adjusting the amplifier volume to show maximum

activity on the screen. Setting the level too low will result in relative analysis

of low frequencies only, while too high a volume shows only high frequency

performance and/or distortion.

After the selection is completed, replay from the start, this time pressing

ceJ for Peak Hold. Press IBl to reset the Peak indicators just before the music starts. After the selection is finished, the Peak indicators show the

maximum average energy reached in each band.

Try replaying the selection, using your tone controls or graphic equalizer to

alter the sound. You can now see the effects of your tone controls or

equalizer on the music by comparing the new peaks to the original peak in

dicators.

Measuring the Audio Chain

Try connecting the Spectrum Analyzer to a low-powered amplifier, such as

the Radio Shack 277-1008A Miniamp, driven by a Realistic 33-1058 Tie Clip

Mike to measure the room and speaker response. Avoid setting the Miniamp

directly on the Color Computer (which can throw off the accuracy of the

measurements). Do not point the microphone directly towards the speakers

(On-axis response). Point the microphone at the ceiling or the floor, but with

the body of the microphone in line with the speakers (Incident response).

7

8

Try the microphone in various parts of the room. Two excellent test posi

tions would be one meter from the speaker (39 inches), and your normal

listening position. Use your tone controls and/or graphic equalizer to try to

match the response achieved in the flat position test from the headphone

output jack.

Summary of Key Commands

[f] - Fast (Real time) display

� · Slow (RMS) averaging display

[Q] - Detail On/Off Full or 1/3 octave

IE] - Peak Hold On/Off

[BJ • Reset Peak Hold

[Al - Audio On/Off through TV

[!SJ - Kaleidoscope On

[ill · Graph On from Kaleidoscope

Space Bar - Freeze Display On/Off

�������������������� � « ?$> RADIO SHACK SOFfW ARE LICENSE � ?$> A. Radio Shack grants to CUSTOMER an non-exclusive, paid up license to ¢� ?$> use on CUSTOMER'S computer the Radio Shack computer software received.

i �$> Title to the media on which the software is recorded (cassette and/or disk) or �

c$> stored (ROM) is transferred to the customer, but not title to the software. ?$ B. In consideration for this license, CUSTOMER shall not reproduce copies of ?$ Radio Shack software except to reproduce the number of copies required for ¢� ��

use on CUSTOMER'S computer (if the software allows a backup copy to be

1�

� made), and shall include Radio Shack's copyright notice on all copies of

� � software reproduced in whole or in part. �

� � ?$> C. CUSTOMER may resell Radio Shack's system and applications software �� -...� (modified or not, in whole or in part), provided CUSTOMER has purchased � C

Radio Shack shall have no liability or responsibility to customer or any other

person or entity with respect to any liability, loss or damage caused or alleged to

be caused directly or indirectly by computer equipment or programs sold by Radio Shack, including but not limited to any interruption of service, loss of business or anticipatory profits or consequential damages resulting from the use

or operation of such computer or computer programs.

RADIO SHACK, A DIVISION OF TANDY CORPORATION

U.S.A.: FORT WORTH, TEXAS 76102 CANADA: BARRIE, ONTARIO L4M 4W6

TANDY CORPORATION

AUSTRALIA BELGIUM U. K.

280-316 VICTORIA ROAD PARC INOUSTRIEL OE NANINNE BILSTON ROAD WEONESBURY

RYOALMERE. N.S.W. 2116 5140 NANINNE WEST MIDLANDS WS10 7JN

Front CoverTitle PageCopyrightsTable of ContentsIntroductionRecommended Input SourcesStarting UpReal-time and RMS Display ModesDetailPeak Hold and ResetFreezing the DisplayAudio OptionKaleidoscope ModeMeasuring the Electronic ChainMeasuring the Audio ChainSummary of Key CommandsRadio Shack Software LicenseBack Cover